Generally, golf balls have been classified as two piece balls or three piece balls. Two piece balls are comprised of a solid polymeric core and a cover. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Three piece balls are comprised of a solid or liquid filled center surrounded by tensioned elastomeric material and a cover. Three piece balls generally have a good "click" and "feel" when struck by a golf club, but are more difficult to manufacture than two piece balls.
The prior art is comprised of various golf balls that have been designed to provide optimal playing characteristics. These characteristics are generally the initial velocity and spin of the golf ball, which can be optimized for various players. For instance, certain players prefer to play a ball that has a high spin rate for playability. Other players prefer to play a ball that has a low spin rate to maximize distance. However, these balls tend to be hard feeling and difficult to control around the greens.
The prior art is comprised of liquid filled golf balls. Wound golf balls have been made with liquid centers for many years. Both U.S. Pat. Nos. 1,568,513 and 1,904,012 are directed to wound golf balls with liquid filled centers. U.S. Pat. Nos. 5,150,906 and 5,480,155, are directed to a hollow spherical shell of a polymeric material which is filled with a liquid or unitary, non-cellular material that is a liquid when introduced into the shell. The shell is disclosed as being the outer cover or an inner layer with the outer cover formed to the external surface thereof. The shell varies in thickness from about 0.060 to 0.410 inches in thickness.
The Rules of Golf as approved by the United States Golf Association (USGA), include the following rules that relate to golf ball construction:
a. Weight
The weight of the ball shall not be greater than 1.620 ounces avoirdupois (45.92 gm).
b. Size
The diameter of the ball shall be not less than 1.680 inches (42.67 mm). This specification will be satisfied if, under its own weight, a ball falls through a 1.680 inches diameter ring gauge in fewer than 25 out of 100 randomly selected positions, the test being carried out at a temperature of 23+/-1.degree. C.
c. Spherical Symmetry
The ball must not be designed, manufactured or intentionally modified to have properties which differ from those of a spherically symmetrical ball.
d. Initial Velocity
The velocity of the ball shall not be greater than 250 feet (76.2 m) per second when measured on apparatus approved by the United States Golf Association. A maximum tolerance of 2% will be allowed. The temperature of the ball when tested will be 23+/-1.degree. C.
e. Overall Distance Standard (ODS)
A brand of golf ball, when tested on apparatus approved by the USGA on the outdoor range at the USGA Headquarters under the conditions set forth in the Overall Distance Standard for golf balls on file with the USGA, shall not cover an average distance in carry and roll exceeding 280 yards (256 m) plus a tolerance of 6%.
The flight of a golf ball is determined by many factors, but only three factors that are typically controlled by the golfer. By impacting the ball with a golf club, the golfer typically controls the speed of the golf ball, the launch angle and the spin rate. The launch angle sets the initial trajectory of the golf ball's flight. The speed and spin of the ball give the ball lift which will define the ball's overall flight path along with the weight and drag of the golf ball. Where the ball stops after being struck by a golf club also depends greatly on the weather and the landing surface the ball contacts.
Many golfers have what is termed a "low swing speed." This means that the club head speed at impact is relatively slow when compared to a professional golfer's. Typically, when driving a golf ball the average professional golf ball speed is approximately 234 ft/s (160 mph). A person having a low swing speed typically drives the ball at a speed less than 176 ft/s (120 mph). Upwards of thirty percent of all golfers today have swing speeds that produce drives of less than 210 yards. A person with a low swing speed has a low ball speed. His or her ball does not fly very far because of the lack of speed and lift.